I've been following along a class about constructors, destructors and constructor overloading in C . (Granted, it's from 2018, I don't know if that changes anything.) Is there any reason that he defines constructors and everything else outside of the class (still inside the same .cpp file)? What's the difference between:

const std::string unk = "unknown";
const std::string prefix = "copy-of-";

class Human {

    std::string _name = "";
    int _height = 0;
    int _age = 0;
    
public: 

    Human();
    Human(const std::string& name, const int& height, const int& age);
    Human(const Human& right);
    Human& operator = (const Human& right);
    ~Human();
    void print() const;
    
};

Human::Human() : _name(unk), _height(0), _age(0) {
    puts("Default Constructor");
}

Human::Human(const std::string& name, const int& height, const int& age)
    : _name(name), _height(height), _age(age) {
    puts("Constructor w/ arguments");
}

Human::Human(const Human& right) {
    puts("Copy Constructor");
    _name = prefix   right._name;
    _height = right._height;
    _age = right._age;
}

Human& Human::operator = (const Human& right) {
    puts("Copy Operator!");
    if (this != &right) {
        _name = prefix   right._name;
        _height = right._height;
        _age = right._age;
    }
}

Human::~Human() {
    printf("Destructor: %s ", _name.c_str());
}

void Human::print() const {
    printf("Hello, I'm %s,